any power supply 1A, 12V for testing (final power supply will be 38-40V)

Change the joins with to not only be press-fit into the aluminium tubes but to have a bolt running across it (into the tube, through the join and out the tube on the other side) to allow for pulling small loads upwards.

Change the effector mount to use a standard ISO-9409-1-50-4-6 (=4xM6 on a 50mm circle)

Have a hole in the center of the mount to allow for cables

Preparation

I know the uStepper Robot Arm is still a Work In Progress.
I hope to get the original CAD files just in time for Easterhegg, so I can design my improvements.
I did get most of the parts from their BoM:

http://www.thingiverse.com/thing:1398215#comment-834544

bearings

5x 608Z

standard skateboard-bearings.

for 8mm shafts

Z=closed on one side.

ZZ=closed on both sides or 608 = open will work too.

5x 625Z

for 5mm shafts(I'm missing these)

10x 624Z

for 4mm shafts

(I did an order of all standard bearings 3mm-8mm a while back. So I *hope* my stock has these covered.)

Nuts

20x M3
7x M4
1x M5
2x M8
(done)

Bolts

The BoM didn't specify the type of head or material for any bolts.
So I tried to stay with hexagonal headed and PH2 ones and tried to stay away from sink-hole bolts.

1x M8x40

used in Fig.10 - use hexagonal head, so you can have the bolt from below and nut on top. Other flat heads mean the nut has to be at the bottom and can fall out on disassembly.

1x M8x70

used as main axis for the large gears

1x M5x40

1x used in Fig.48

4x M4x20

2x used in Fig.55

1x used in Fig.56

1x used in Fig.57

1x M4x30

1x used in Fig.55

1x M4x35

1x used in Fig.63

1x M4x55 substituted M4x60 as 55mm was not avaliable.

1x used in Fig.65

15x M3x8 substituted M3x10 counter sunk head

use 4x (M3x10) in Fig.29

use 4x (M3x10) in Fig.31

use 4x (M3x10) in Fig.33

TODO: where to the other 3 go?

2x M3x10 substituted M3x10

2x used in Fig.25 - longer is okay. Any flat head type.

4x M3x12 substituted M3x16

4x used in Fig.9 - must be 11-13mm, head must have at most 5mm diameter

7x M3x20

5x used in Fig.3 - any flat head. steel brass or aluminium but even plastic bolts are okay.

2x used in Fig.21 - indended maximum head diameter 5mm but larger ones work if the head is at most 3mm in height

4x M3x30

4x used in Fig.44

Washers

5x M8 OD=15,8mm
4x M5 OD=9,8mm
2x M4 OD=8.8mm
I didn't find ANY of these sizes. So I hope grabbing large and small washers for M4,M5 and M8 from my stock will do.

Spacers

1x 14m (update: inner diameter just wider then M8 threads)
1x 7mm (update: inner diameter just wider then M4 threads)
Didn't find any because the BoM doesn't specify what kind of spacers they talk about.
I can't find them on the image nor the instructions.

Update: found them. Fig.36 has a typo and speaks of "space" instead of "spacers". Aparently they must have an inner diameter to fit an M8 and M4 bolt loosely.

tubes

The instructions don't specify if they talk about the outher or inner diamter
and what wall thickness is expected. (Clearly as seen in figure 20 and 22, inner AND outher diameter are important.)

1x 15x300 I got 1m of 16x1mm, it seems to be a snug fit in Gears_main_arm_15mm.stl, large_joins.stl fits but is a bit loose
1x 15x220
2x 6x240 I got 1m of 6x1mm
1x 6x252

...as you can see. The pure number of DIFFERENT bolt sizes is staggering.

Progress

Done:

sourcing all nuts and bolts (some bolts replaced by longer versions)

cutting tubes to length

assembled the first parts. List of suggestions for improvements is growing...

Written the source code that will rund this arm using G-Code to control
L6470 chips.

Assembled the original design as far as I can without the 625Z bearings.

M3x20 is for Fig.3 and ??? any flat head. steel brass or aluminium but even plastic bolts are okay.

...

name where longer versions of bolts are acceptable and up to what length

name and show all dimensions for spacers (one is for M8, the other for M5)

Fig.1: a 608 (no covers) would do just as well as a 608z(cover on one side) or 608zz (covers on both sized)

Fig.2: prepare how? What am I supposed to do in this step?

Fig.3: no comment

Fig.4 use M3x20.

Fig.5: no comment

Fig.6: use a sturdy table to help press-fit the 608Z or 608ZZ skateboard bearing

Fig.7: "prepare" means "insert M3 nuts"

Fig.8: this is "side2.stl", not "side1.stl"

Fig.9: use M3x12 (at most 13mm) to mount the sides to the base?

Fig.10: use M8x40mm

M8 x 40mm

Fig.11: add an M8 washer of 9-12mm (if not included as a feature of base.stl)

Fig.12: use M3x8mm(M3x10 works too) to mount the small gear to the motor-shaft

Fig.13:

M3x10 is too short for the NEMA17 motor but the M3x8 are the only ones we have >12pcs of ??? (same for Fig.29+31. Question asked here)

you may want to do this before Fig.12 because the mounted motor determines where on the shaft the gear has to be

Fig.14: no comment

Fig.15: no comment

Fig.16: no comment

Fig.17: use a sturdy table to help press-fit the 608Z or 608ZZ skateboard bearing

Fig.18: no comment

Fig.19

Is this large_joint.stl ?

The "main arm" the short 15mm pipe

Fig.20: use glue and/or a drill and an additional M3x20 with a self-locking M3 nut

Fig.21: use M3x20mm

Fig.22: no comment

Fig.23:use a sturdy table to help press-fit the 608Z or 608ZZ skateboard bearing

Fig.24 TODO: I seem to be missing 624Z or 624ZZ bearings

Fig.25: use M3x10mm

Fig.26: no comment

Fig.27: TODO: what size of washers?

Fig.28:

use M3x8mm(M3x10 works too)

don't forget about the M3 nut (hole is slightly larger then M3)

use the thinner one of the 2 small gears

Fig.29: use 4x M3x10mm, make use of the recess for the bolt-heads

Fig.30:

use M3x8mm(M3x10 works too) to mount the small gear to the motor-shaft

use the wider one of the 2 small gears

Fig.31: use 4x M3x10mm, make use of the recess for the bolt-heads

Fig.32: this is needed because you can't reach all 4 motor-bolts with the main gear on

Fig.33: use 4x M3x10mm, make use of the recess for the bolt-heads

Fig.34: no comment

Fig.35: no comment

Fig.36

"space" should be "spacer"

Spacer is 14mm long and fits around an M8 bolt

Fig.38 one washer between gear and side plate is plenty

...

Fig.44:

use 4x M3x30mm, bolt heat must be <4mm in diameter

bracket_part1.stl

bracket_part2.stl

Fig.45: nothing to do here

Fig.46: nothing to do here

Fig.47 see comment for Fig.48

Fig.48 why M5? It's the only 5mm bolt in the entire construction and introduces an entirely new type of ball bearing. M4 would have worked just the same.

Fig.49 one washer on the bearing, the other where the bolt exits

Fig.50 one washer where the bolt exits

Fig.51 this should be a nylon locking nut or else it will shake loose.

Fig.52: nothing to do here

Fig.53: nothing to do here

Fig.54: nothing to do here

Fig.55

use 1x M4x30 on the secondary arm joint

use 2x M4x20 on the 2 rods that connect to the triangle

TODO: Where to put what rod-length and what side to mount to (inside/outside)

Fig.56

use 1x M4x20 on the rod that connect to the triangle

Fig.57: use 1x M4x20

Fig.58: nothing to do her

Fig.59: nothing to do here

Fig.60: no comment

Fig.61: nothing to do here

Fig.63: use M4x35

Fig.64

Fig.65: use M4x55 (or longer)

Fig.66: finished! (with the mechanical hardware)

Notes about improvements:

holes for bolts should have a camfer to make inserting bolts easier by having them self-align.

the holes for the 608 bearings work surprisingly well without them but it would still be a good idea since not every printer produces dimensionally accurate results.

labeling the holes with the bolt-sizes costs nothing in 3d printing.

use less different bolt sizes

name bolt sizes in assembly steps

all parts are very low resolution. Lots of clearly visible polygon-edges.

Gears are a highly simplified design. They however do have only little backlash.

...

base.stl

M3 bolt-holes too small. 3.1mm would be better.

M3 nut-holes could use a camfer (any stray sterand of filament makes this harder).

my bolts have a 6mm wide head. The hole is 5mm. Wider heads should be supported.

Make M8 hole smaller to allow for M8 washer of 9-12mm to sit on bottom 608/608Z/608ZZ bearing OR include that washer as a feature of the base.stl design

Gears_bottom_edited_plus10.stl

M3 bolt-holes too small. 3.2mm would be better (slightly larger then the hole in the side that holds the nut).

nuts are inserted too deep. You can't align them after having them fall down the shaft to meet the bolt.

side_plate1.stl

is a very tight fit into base.stl

a tapper on the nuts that slide into base.stl coult also help.

holes for M3 nuts should be hexagonal and closed on one side to prevent the tiny bolt from slipping out. (This isn't laser-cutting.)

move the bolt that doesn't go through the bottom gear further outwards, so it can be removed without having to disassemble the bottom gear.

Gears_main_arm_15mm.stl

camfer for 3mm bolts needed. Any stray strand of filament makes this harder then it needs to be

label the gear "main gear"

Gears_second_arm.stl

no tapper for M5 nuts

mirror the small gear to have the bolt on the inside of the machine (accessible from above). That way it won't interfere with a longer bolt in the side_plates and the side plate can be made stronger by not having the access tunnes for this bolt.

second_gear_arm.stl

no hexagonal holes for the M3 nuts. They may shake loose.

link.stl

M4 hole is too tight

large hole needs camfer. Hard to inser.

A flat instead of round end should make push-fitting the rod with force easier

triangle.stl

M3 holes definately need a camfer

convert to use M4 and get rid of the 625Z bearing size in favor of only using 624Z

end_part3.stl

integrate the M4 spacer into this part

bracket_part1.stl

wider brace to allow for 16mm aluminium rods

convert to use M4 and get rid of the 625Z bearing size in favor of only using 624Z

bracket_part2.stl

should have a slightly wider holt then bracket_part1.stl , so the bolt fastens properly in the plastic

should allow for wider bolt-heads

wider brace to allow for 16mm aluminium rods

convert to use M4 and get rid of the 625Z bearing size in favor of only using 624Z

Software

I'm planning to use this trivial Arduino G-Code parser, throw out the Bresenham line algorithm (since we need not generate step+dir pulses ourself) to instead feed tool-coordinates into the
L6470 Autodriver boards.